1. Field of the Invention
The present invention relates to a stereoscopic image display method and a stereoscopic image display apparatus using the same and, more particularly, to a stereoscopic image display method using a spatial light modulation element as a parallax barrier or a slit pattern for controlling the directivity of light coming from backlight, and a stereoscopic image display apparatus using the method.
2. Related Background Art
The technique of a stereoscopic image display method using a parallax barrier method is disclosed by S. H. Kaplan ("Theory of Parallax Barriers", J.SMPTE, Vol. 59, No. 7, pp. 11-21, 1952). In this method, each of a plurality of parallax images is divided into stripe pixels, the stripe pixels constituting the right and left parallax images are alternately arranged on a single screen to form and display a stripe image, and the corresponding parallax images are observed by the right and left eyes of an observer via a slit (called a parallax barrier) which is arranged at a position separated by a predetermined distance from the stripe image and has predetermined light-transmission portions, thereby obtaining a stereoscopic view.
However, such conventional apparatus cannot be used as a two-dimensional image display apparatus such as a normal television apparatus.
In view of this problem, Japanese Patent Application Laid-Open Nos. 3-119889 and 5-122733 disclose a stereoscopic image display apparatus, which electronically forms a parallax barrier using, e.g., a transmission type liquid crystal element, and electronically controls to change the shape and positions of barrier stripes.
FIG. 34 is a schematic diagram of a stereoscopic image display apparatus disclosed in Japanese Patent Application Laid-Open No. 3-119889. In this apparatus, an electronic parallax barrier 103 comprising a transmission type liquid crystal display element is arranged on an image display surface (panoramagram or stereogram) 101 via a transparent glass/acrylic spacer 102 having a thickness d. A plurality of parallax images obtained by picking up an image from two or more directions are displayed on the image display surface 101 as a stripe image obtained by dividing each of the parallax images into vertical stripe pixels, and alternately arranging the stripe pixels of the plurality of parallax images in a predetermined order. On the other hand, vertically elongated barrier stripes are formed at arbitrary positions on the display surface of the electronic parallax barrier 103 by designating the X and Y addresses of the parallax barrier 103 using a control means such as a microcomputer 104, thus allowing a stereoscopic view according to the principle of the parallax barrier method.
In order to display a two-dimensional image (non-stereoscopic image) on this apparatus, the entire image display region of the electronic parallax barrier 103 is set in a transparent state without forming any barrier stripes thereon. In this manner, both stereoscopic and two-dimensional images can be displayed unlike in the stereoscopic image display method using the conventional parallax barrier method.
FIG. 35 is a schematic sectional view showing principal part of a stereoscopic image display apparatus constituted by a liquid crystal display panel and an electronic barrier disclosed in Japanese Patent Application Laid-Open No. 5-122733. In this stereoscopic image display apparatus, two liquid crystal layers (TN) 115 and 125 are respectively sandwiched between two pairs of polarizing plates 111 and 118, and 121 and 128, so that the liquid crystal layer 115 serves as an image display means, and the liquid crystal layer 125 serves as an electronic barrier forming means. Note that the apparatus shown in FIG. 35 also comprises a glass (spacer) 102, upper glass substrates 112 and 122, lower glass substrates 117 and 127, common electrodes 113 and 123, spacers 114 and 124, and pixel electrodes 116 and 126. In this apparatus as well, in order to display a two-dimensional image (non-stereoscopic image), the entire image display region of the electronic parallax barrier 125 is set in a transparent state without forming any barrier stripes thereon. In this manner, both stereoscopic and two-dimensional images can be displayed.
In the prior art disclosed in Japanese Patent Application Laid-Open No. 3-119889, the image display surface 101 displays a single stripe image obtained by dividing at least two parallax images into stripe pixels and alternately arranging the stripe pixels of these two parallax images. Therefore, the stereoscopic resolution of the image display apparatus is reduced to at least 1/2 that of original parallax images.
Furthermore, in the above-mentioned prior art, since the stripe image constituted by the vertical stripe pixels displayed on the image display surface 101 is not synchronized with the parallax barrier pattern formed on the electronic parallax barrier 103, crosstalk between the right and left images is generated, and flicker noise is often generated, resulting in an eyesore.
On the other hand, since the display positions of the barrier stripes remain the same unless the view point position of the observer moves, the luminance decreases in a localized stripe pattern.
Furthermore, when the image display means comprises, e.g., a liquid crystal, the image display surface has a stripe-shaped pixel structure, and such image must be observed via similar barrier stripes, thus easily causing Moire fringes.
Furthermore, in the prior art disclosed in Japanese Patent Application Laid-Open No. 5-122733, since the apparatus uses a total of four polarizing plates, the luminance lowers due to absorption by these plates.
In addition, in these prior arts, when the observer horizontally moves by only the interval between his or her eyes (inter-ocular distance), a pseudoscopic view is prevented by replacing the display positions of the right and left eye images of the stripe image. However, the apparatus cannot cope with a change in view point position in the back-and-forth direction with respect to the apparatus.
Furthermore, in order to prevent the pseudoscopic view, a change in view point position of the observer is followed so that normal parallax images are always incident on the eyes, and the observed stereoscopic image always remains the same. Thus, a "roundabout or wraparound stereoscopic view effect" that can obtain smooth stereoscopic feeling cannot be obtained.